smtp transport: poll for trailing data to drain before close

[exim.git] / src / src / transports / smtp.c

diff --git a/src/src/transports/smtp.c b/src/src/transports/smtp.c
index ee07bcfe87dbd2155045c70c7d58559cac69443a..721056f278978bf5aa30b3471e53ff33d032e855 100644 (file)
--- a/src/src/transports/smtp.c
+++ b/src/src/transports/smtp.c
@@ -4810,8 +4810,11 @@ if (sx->send_quit || tcw_done && !tcw)
     sx->cctx.tls_ctx = NULL;
     }
 #endif
-  millisleep(20);
-  if (fcntl(sx->cctx.sock, F_SETFL, O_NONBLOCK) == 0)
+
+  /* Drain any trailing data from the socket before close, to avoid sending a RST */
+
+  if (  poll_one_fd(sx->cctx.sock, POLLIN, 20) != 0            /* 20ms */
+     && fcntl(sx->cctx.sock, F_SETFL, O_NONBLOCK) == 0)
     for (int i = 16, n;                                                /* drain socket */
         (n = read(sx->cctx.sock, sx->inbuffer, sizeof(sx->inbuffer))) > 0 && i > 0;
         i--) HDEBUG(D_transport|D_acl|D_v)